TCP sendto removal + error when UDP for hostnames (#2414)

- UDP inet_pton(remote_ip)'s result is not checked -> the server ends up
  sending packets to the null address when a hostname is given instead
of a IPv4 address. A error is now raised

- TCP is using sendto() instead of send(). We can thus remove a useless
inet_pton() call (which moreover differs from the gethostbyaddr used in
setup_port() - possible issues when using hostnames)

Signed-off-by: Benoit Maurin <[email protected]>

src/mavsdk/core/tcp_client_connection.cpp

@@ -163,16 +163,11 @@ bool TcpClientConnection::send_message(const mavlink_message_t& message)
     auto flags = MSG_NOSIGNAL;
 #endif
 
-    const auto send_len = sendto(
-        _socket_fd.get(),
-        reinterpret_cast<char*>(buffer),
-        buffer_len,
-        flags,
-        reinterpret_cast<const sockaddr*>(&dest_addr),
-        sizeof(dest_addr));
+    const auto send_len =
+        send(_socket_fd.get(), reinterpret_cast<const char*>(buffer), buffer_len, flags);
 
     if (send_len != buffer_len) {
-        LogErr() << "sendto failure: " << GET_ERROR(errno);
+        LogErr() << "send failure: " << GET_ERROR(errno);
         _is_ok = false;
         return false;
     }

src/mavsdk/core/udp_connection.cpp

@@ -77,7 +77,10 @@ ConnectionResult UdpConnection::setup_port()
 
     struct sockaddr_in addr {};
     addr.sin_family = AF_INET;
-    inet_pton(AF_INET, _local_ip.c_str(), &(addr.sin_addr));
+    if (inet_pton(AF_INET, _local_ip.c_str(), &(addr.sin_addr)) != 1) {
+        LogErr() << "inet_pton failure for address: " << _local_ip;
+        return ConnectionResult::SocketError;
+    }
     addr.sin_port = htons(_local_port_number);
 
     if (bind(_socket_fd.get(), reinterpret_cast<sockaddr*>(&addr), sizeof(addr)) != 0) {
@@ -129,7 +132,11 @@ bool UdpConnection::send_message(const mavlink_message_t& message)
         struct sockaddr_in dest_addr {};
         dest_addr.sin_family = AF_INET;
 
-        inet_pton(AF_INET, remote.ip.c_str(), &dest_addr.sin_addr.s_addr);
+        if (inet_pton(AF_INET, remote.ip.c_str(), &dest_addr.sin_addr.s_addr) != 1) {
+            LogErr() << "inet_pton failure for address: " << remote.ip;
+            send_successful = false;
+            continue;
+        }
         dest_addr.sin_port = htons(remote.port_number);
 
         uint8_t buffer[MAVLINK_MAX_PACKET_LEN];